As the demands for energy increases, solar cells that convert solar energy into electric energy are being actively developed. Among the color cells, a solar cell using a silicon wafer is being widely and commercially used.
Specifically, the silicon wafer includes an PN junction in which an N+ layer and a P layer adhere to each other and a back surface field (BSF) layer that is a P+ layer. Here, the BSF layer may reduce a contact resistance with a rear contact to improve characteristics of the solar cell. Thus, as the BSF layer increases in thickness, the performance of the solar cell may be improved.